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force index problem in 8.4.1

From: Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>
To: Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: force index problem in 8.4.1
Date: 2009-11-25 22:35:55
Message-ID: Pine.LNX.4.64.0911260124500.6801@sn.sai.msu.ru (view raw or flat)
Thread:
Lists: pgsql-hackers
Hi there,

I tried to force query to use index by specifying high execution cost, but
without success, even seqscan cost doesn't changed. This is 8.4.1

=# explain select count(*) from spots where coordinates <@ '(0,0),(0.1,0.1)'::box;
                              QUERY PLAN 
--------------------------------------------------------------------
  Aggregate  (cost=26620.84..26620.85 rows=1 width=0)
    ->  Seq Scan on spots  (cost=0.00..25328.12 rows=517085 width=0)
          Filter: (coordinates <@ '(0.1,0.1),(0,0)'::box)
(3 rows)

Time: 1.944 ms
=# alter FUNCTION pt_contained_box(point, box) COST 10000;
ALTER FUNCTION
Time: 369.800 ms
=# explain select count(*) from spots where coordinates <@ '(0,0),(0.1,0.1)'::box;
                              QUERY PLAN 
--------------------------------------------------------------------
  Aggregate  (cost=26620.84..26620.85 rows=1 width=0)
    ->  Seq Scan on spots  (cost=0.00..25328.12 rows=517085 width=0)
          Filter: (coordinates <@ '(0.1,0.1),(0,0)'::box)
(3 rows)

Time: 0.891 ms


 	Regards,
 		Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83

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